The invention relates to apparatus for opening and cleaning fibrous material. More particularly the invention relates to the removal of dust from fibrous material.
In a previously known opening and cleaning apparatus as shown in U.S. Pat. No. 2,844,847 there is disclosure of an arrangement of this kind including above the beaters a large dust chamber separated from the beaters by an inclined perforated screen. A disadvantage occurs in this arrangement as it relies on a high amount of suction applied to the exhaust duct located in the topmost wall of the chamber to lift the dust and trash away to waste. Such an arrangement is very inefficient in operation in that short fibres passing through the screen pill together in the air currents and do no lift from the chamber and consequently a blockage can result which will prevent proper functioning of the machine.
U.S. Pat. No. 4,025,989 also discloses a similar arrangement of an opener and cleaner for fibrous materials in which a dust chamber is provided over a beater arrangement and a suction source is connected to an exhaust outlet in the topmost wall of the dust chamber. Separate guide plates are positioned above each beater, these being provided with perforations for the extraction of fine dust from the material being processed. These perforated guide plates do not form a continuous screen to prevent material being processed from being flung upwardly into the dust chamber. This arrangement is disadvantageous in that in some situations usable fibres can be extracted along with unusable fibres and dust through the suction outlet. Additionally it is difficult to properly separate dust from the fibres and in some arrangements very little dust is withdrawn through the exhaust outlet.
In the above disclosures of the prior art it is difficult to remove dust without causing short unusable fibres to interfere with the proper function of the machine. Additionally it is also difficult to extract dust without extracting usable fibres and in some cases, difficult to extract an adequate percentage of dust.
It is therefore an object of our invention to provide apparatus and a method of extracting dust and unusable fibres in a more efficient manner.